Solid-state imagers are finding increased use in cameras for detecting radiant energy in the visible and infrared light range due to their long life, low power consumption and small size, as compared with conventional image pick-up tubes. Such solid-state imagers include commercially available charge-coupled devices (CCD), charge-injection devices (CID) and metal-oxide-semiconductor (MOS) devices which have been designed for use in television cameras for producing color television signals. Television cameras may use a single imager in combination with a color encoding filter having a stripe or checkerboard pattern or a plurality of imagers, each imager being located at a different light output port of color separation optics.
The fabrication of solid-state imager devices is typically based on silicon technology. The spectral response of silicon solid-state imagers extends to wavelengths longer than those visible to the human eye. That is, the human eye reponse drops off for wavelengths greater than 700 nm while the response of silicon imaging devices extends to approximately 1100 nm. As a result, in a color or black and white television camera including silicon images, it is necessary to include an infrared (IR) rejection filter in the camera optical path so as to obtain correct colorimetry or contrast in the picture reproduced from the imager-developed signal.